MP4653—REAL LIPS CC/CV MODE LLC TV LED DRIVER

MP4653 Rev 1.01

www.MonolithicPower.com

20

6/28/2012

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2012 MPS. All Rights Reserved.

APPLICATION INFORMATION

Setting the LED Current (Pin7, IFB)

The external LED current sensing resistor sets

the maximum LED current (refer to TYPICAL

APPLICATION CIRCUIT) and value can be

determined using the equation:

LED

0.2V

Rsense

I



The ILED is the total current of the LED strings.

It is recommended a 1k resistor between the IFB

pin and the current sensing resistor for short

proteciton.

Setting the minimum/maximum operating

frequency (Pin1 SS, Pin2 FSET)

The

operating

frequency

of

MP4653

is

determined by the sourcing current through SS

pin and FSET pin.

9

FSET

op

SS _ FSET

FSET

V

21.49V

f(

) 1.98 10

RR









outputs of internal amplifiers for voltage loop and

current loop. It is in range of 1~2.2V.

The minimum operating frequency is set by:

9

min

SS _ FSET

FSET

21.49V

2.2V

f(

) 1.98 10

RR









The maximum operating frequency is set by:

9

max

SS _ FSET

FSET

21.49V

1V

f(

) 1.98 10

RR









Setting the Soft Start up Frequency and Soft

Start Time (Pin1 SS)

The soft start up frequency is:

SS _ FSET

SS

9

s_ start

SS _ FSET

SS

FSET

21.49V (R

R )

1V

f(

) 1.98 10

R* R

R











Usually, the soft start up frequency could be 1.5

to 3 times of the maximum operating frequency.

The soft start time is determined by the RC

could be estimated with 3 times of the RC

Constant:

SS

SS

SS

T3 R

C





Setting the Voltage Loop Feedback (Pin4 VFB)

The voltage on VFB pin should between 1.2V

and 2V at normal operation. Set the voltage

sure the feedback voltage is in this range at

normal operation.

VFBL

VFB

bus

VFBH

VFBL

R

1.2V

V

V

2V

RR









The VFB pin also functions as the over voltage

protection for the bus stage. When the voltage on

VFB gets higher than 2.4V, IC triggers bus stage

protection.

Setting Over-Voltage Protection of the LED

Stage (Pin9,10,11,12)

The voltage divider sets the over-voltage

protection

point

(refer

to

TYPICAL

APPLICATION CIRCUIT) through the equation:

OVPH

OVPL

OVP

OVPL

RR

V2.4V

R





Normally, the OVP point is setting about 10%-

30% higher than the maximum LED voltage.

Setting the Voltage Difference Protection of

the LED Strings (Pin9,10,11,12)

MP4653 implements the protection when LED

string voltage is different from each other, in

order to protect the condition that several LEDs

in a string are shorted. It is used only for multiple-

strings application. The protection point of the

voltage difference between LED strings is set by:

input

OVPH

OVPL

pro

OVPL

23k R

RR

V2.4V

R16 23k













pin. Adjust the input resistance to program the

protection point.

voltage divider and LED# pins to adjust the input

resistance.

OVPH

OVPL

input

X

OVPL

OVPH

RR

RR

RR





